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Successful Tracking of Reservoir Sand Geometry and Its Characterization Through Wire Line Logs - A Case Study

Veerubhotla L. Avadhani, S Rama Murty Pantulu, Kiran Kant Prasad, and Om Prakash Srivastava
CEWELL, ONGC Ltd, Vadodara, India

Mori Field, of KG Basin India, hosts many sand reservoirs, which are vertically stacked over an interval of 1100m but show deceptive aerial extent. Encased in a SW-NE trending Faults in a narrow corridor and distributed over two different depositional and pressure regimes, these sands pose exciting challenge for tracking their geometry. An integrated approach is presented to bring out the lateral distribution of one such reservoir using all the wire line log data and geological observations in this study.

Multivariate log correlations are carried out to deduce the lateral facies variation of identified stratal units with good confidence. Structural disposition of the sand is mapped and isopachs and isoliths of the sand body are prepared which indicated preferential reservoir depositional locales. Processing of Formation Micro Imaging data, interactive dip picking and its interpretation by conventional and Bengtson’s technique helped in modeling the reservoir as a set of bar sands and deducing their orientation. The coalescing nature of these bars is brought out by slicing and mapping the cumulative sand percentages. This nature of the reservoir explained the hydrodynamic discontinuity of the reservoir observed during the testing of the sand. Acoustic impedance computation from log data and separation of the reservoir and non-reservoir rocks in impedance domain gave much needed link to convert seismic facies to reservoir facies and mapping them.

The adopted methodology provided the depositional model of the reservoir sand through wire line data in consistence with geological understanding of the area and observed testing data. Identifying the prospective areas for detailed seismic mapping for other interesting reservoirs along with and providing inputs for building exploration model with seismic data for the reservoir under study are the other value additions.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery